Ramón J. Durán

Dynamic Routing and Wavelength Assignment in Optical Networks by Means of Genetic Algorithms

We propose a novel genetic algorithm for solving the dynamic routing and wavelength assignment (DRWA) problem in wavelength-routed optical networks. The algorithm not only obtains low call blocking probability, but it also employs a very short computation time. Moreover, it is capable of providing fairness among connections, that is, to offer approximately the same quality of service (in terms of blocking probability) for all source-destination node pairs. Since requirements on optical network availability are highly severe, we also propose an extension of the algorithm to provide fault-tolerance capability at the optical layer. It is achieved by means of protection, where each optical connection request is provided with a pair of lightpaths (a primary and a backup lightpath). Again, the genetic algorithm proves to be highly efficient, in this case, at performing routing and wavelength assignment of pairs of lightpaths.

A Cognitive Quality of Transmission Estimator for Core Optical Networks

We propose a cognitive Quality of Transmission (QoT) estimator for classifying lightpaths into high or low quality categories in impairment-aware wavelength-routed optical networks. The technique is based on Case-Based Reasoning (CBR), an artificial intelligence technique which solves new problems by exploiting previous experiences, which are stored on a knowledge base. We also show that by including learning and forgetting techniques, the underlying knowledge base can be optimized, thus leading to a significant reduction on the computing time for on-line operation. The performance of the cognitive estimator is evaluated in a long haul and in an ultra-long haul network, and we demonstrate that it achieves more than 98% successful classifications, and that it is up to four orders of magnitude faster when compared with a non-cognitive QoT estimator, the Q-Tool.

Hybrid RSS-RTT localization scheme for indoor wireless networks

Nowadays, a variety of information related to the distance between two wireless devices can be easily obtained. This paper presents a hybrid localization scheme that combines received signal strength (RSS) and round-trip time (RTT) information with the aim of improving the previous localization schemes. The hybrid localization scheme is based on an RSS ranging technique that uses RTT ranging estimates as constraints among other heuristic constraints. Once distances have been well estimated, the position of the mobile station (MS) to be located is estimated using a new robust least-squared multilateration (RLSM) technique that combines the RSS and RTT ranging estimates mitigating the negative effect of outliers. The hybrid localization scheme coupled with simulations and measurements demonstrates that it outperforms the conventional RSS-based and RTT-based localization schemes, without using either a tracking technique or a previous calibration stage of the environment.

Cognitive dynamic optical networks [invited]

The use of cognition is a promising element for the control of heterogeneous optical networks. Not only are cognitive networks able to sense current network conditions and act according to them, but they also take into account the knowledge acquired through past experiences; that is, they include learning with the aim of improving performance. In this paper, we review the fundamentals of cognitive networks and focus on their application to the optical networking area. In particular, a number of cognitive network architectures proposed so far, as well as their associated supporting technologies, are reviewed. Moreover, several applications, mainly developed in the framework of the EU FP7 Cognitive Heterogeneous Reconfigurable Optical Network (CHRON) project, are also described.

Implementation of a PID controller for the bandwidth assignment in long-reach PONs

In this paper a proportional-integral-derivative (PID) controller to efficiently allocate bandwidth in high coverage passive optical networks (PONs) is presented. The novelty of this proposal relies on the fact that this is the first proposal to use a PID to control a network parameter in PONs. As the PID takes into account present, past and possible future errors in the bandwidth adjustment, this self-adapting technique results in a very robust process. Simulation results exhibit that not only is it faster and more stable than other algorithms, but also it auto-adapts the resources very efficiently when facing real time changes in the network parameters or in the bandwidth conditions. In fact, the standard deviation of the difference between the allocated and the guaranteed bandwidth is reduced by up to 50% and the convergence speed is up to four times quicker than other proposals.

Polymorphic architectures for optical networks and their seamless evolution towards next generation networks

This paper proposes a novel polymorphic framework for optical networking and a seamless evolution path from optical circuit-switched towards optical packet-switched networks. We show that by simultaneously supporting several optical switching paradigms in a single physical topology, efficient and flexible optical networks can be built. The supported paradigms are associated with different Classes of Service (CoS) in order to provide service differentiation at the optical layer. Two polymorphic architectures are presented, one based on optical circuit switching paradigms with different grades of dynamism, and a second one based on optical labeled burst-switched networks with the added capability of dynamic lightpath provisioning. These architectures provide a seamless evolution path towards an efficient IP-over-WDM approach with service differentiation. Moreover, the proposed polymorphic architectures are fully compatible with the GMPLS unified control plane. We present in a detailed form the proposed polymorphic framework, including the selection of switching paradigms, its support for CoS, the network and control architecture, and a possible seamless evolution towards optical packet-switched networks. Possible implementation examples of optical network nodes that support the proposed polymorphic architectures are also presented.

A bandwidth assignment polling algorithm to enhance the efficiency in QoS long‐reach EPONs

A novel polling algorithm is proposed to provide subscriber differentiation at the upstream channel in long-reach EPONs. As operators and service providers prefer to operate at loads with no congestion and losses, the developed algorithm has been designed to improve the efficiency for those loads at which the network is likely to work. This new scheme permits to anticipate the transmission of some packets in order to take advantage of the wasted bandwidth between consecutive transmissions of ONUs. As a result, not only does this algorithm behave alike other polling algorithms for high loads, but it also improves the efficiency at low and medium loads, leading to a reduction in the mean packet delay. The new algorithm has been tested in different scenarios, motivated by the increasing interest in enlarging the long-reach EPON distances. Simulation results show that as the distance increases, the algorithm achieves a significant reduction of the mean packet delay for an extended range of loads. Copyright

Genetic Algorithm for Joint Routing and Dimensioning of Dynamic WDM Networks

The dynamic operation of WDM networks might lead to significant wavelength savings, when compared with their static counterpart, at the expense of facing nonzero blocking probability. Hence, efficient dimensioning (i.e., determining each link capacity) and control methods are required to operate these networks. Typically, the dimensioning of WDM networks is carried out only after the routing algorithm has been defined. However, this way of designing the network might result in inefficient solutions in terms of wavelength requirements. We propose a novel genetic algorithm to solve the joint routing and dimensioning problem in dynamic WDM networks, with the aim of obtaining a network cost close to minimum while guaranteeing an upper bound on the blocking probability. Used prior to network operation, the algorithm determines which route should be used for each potential connection and also dimensions the number of wavelengths required in each link. The efficiency of the algorithm is validated in ring and mesh topologies, providing wavelength savings of up to 17% when compared with the best existing algorithm to date. Moreover, since the routes provided by the genetic algorithm are stored in routing tables, it also ensures extremely fast on-line network operation.

Accurate and integrated localization system for indoor environments based on IEEE 802.11 round-trip time measurements

The presence of (Non line of Sight) NLOS propagation paths has been considered the main drawback for localization schemes to estimate the position of a (Mobile User) MU in an indoor environment. This paper presents a comprehensive wireless localization system based on (Round-Trip Time) RTT measurements in an unmodified IEEE 802.11 wireless network. It overcomes the NLOS impairment by implementing the (Prior NLOS Measurements Correction) PNMC technique. At first, the RTT measurements are performed with a novel electronic circuit avoiding the need for time synchronization between wireless nodes. At second, the distance between the MU and each reference device is estimated by using a simple linear regression function that best relates the RTT to the distance in (Line of Sight) LOS. Assuming that LOS in an indoor environment is a simplification of reality hence, the PNMC technique is applied to correct the NLOS effect. At third, assuming known the position of the reference devices, a multilateration technique is implemented to obtain the MU position. Finally, the localization system coupled with measurements demonstrates that the system outperforms the conventional time-based indoor localization schemes without using any tracking technique such as Kalman filters or Bayesian methods.

Cognition to design energetically efficient and impairment aware virtual topologies for optical networks

“Greening the Internet” is an important research topic in the last years. The Internet capacity and energy consumption have increased, and the utilization of design and operation techniques to reduce this consumption are a must. In this paper, we present a multiobjective genetic algorithm to design virtual topologies for reconfigurable wavelength-routed optical networks with the aim of reducing both the energy consumption and the network congestion while ensuring that the lightpaths of the virtual topologies fulfill quality of transmission requirements. Moreover, we also present another version of that method enhanced with cognitive techniques, and we show, by means of simulation, the performance advantages brought when introducing these cognitive techniques.